Rape stem weevil

Systematic position: The rape stem weevil (Ceutorhynchus picitarsis) belongs to the order Coleoptera and the family Curculionidae. It is a well-known agricultural pest that specializes in cruciferous plants, primarily affecting large-scale oilseed rape farming.

Crops damaged: The primary host for this pest is oilseed rape (Brassica napus). It also infests other cruciferous plants, including both cultivated mustard varieties and wild weeds, which serve as alternative food sources for the insect during certain stages of its life cycle.

Biology and life cycle: Adult weevils overwinter in the soil or under debris at the edges of fields. When spring temperatures rise to approximately 6-9°C, they emerge to feed on the young leaves and shoots of the rape. Females lay their eggs within the stems of the host plants, where the larvae develop, feed on internal tissues, and eventually drop to the ground to pupate.

Damage and economic significance: The economic damage is caused by the larval stage tunneling inside the stems. These tunnels disrupt the plant's vascular system, hindering the transport of nutrients and water. This often results in stunted growth, increased susceptibility to secondary infections, reduced winter hardiness, and significant yield loss at harvest time.

Protection measures: Management strategies emphasize the prevention of early infestations. Farmers should utilize crop rotation to break the cycle of the pest. Regular field scouting using yellow water traps is essential for detecting the initial migration of adults. If the population exceeds the economic threshold, the application of systemic insecticides is the standard practice to prevent larval establishment.